A composite video signal transmitted within a television broadcasting system is a synthesized signal which comprises a luminance signal, a chrominance signal, a vertical sync signal, and a horizontal sync signal. Furthermore, the composite video signal has a vertical blanking interval which does not contain any data that is used to reproduce the video signal. As a result, time code data may be inserted into the vertical blanking interval, and such time code data may be extracted from such interval during an editing process in order to more easily edit the video signal.
The time code data may include a vertical interval time code VITC which relates to a particular standard created by the Society of Motion Picture and Television Engineers ("SMPTE"). For example, the time code VITC may correspond to the National Television System Committee ("NTSC") broadcasting system. In such system, a video signal contains 525 lines per picture and has a flash rate of 60 Hz, and the time code data is inserted in the vertical blanking intervals for lines 7-17 and lines 270-279. Alternatively, the time code VITC may correspond to the Phase Alteration Line ("PAL") broadcasting system. In such system, a video signal contains 625 lines per picture and has a flash rate of 50 Hz, and the time code data is inserted in the vertical blanking intervals for lines 6-22 and lines 319-335.
The vertical interval time code VITC may comprise nine 2-bit sync signals, nine 8-bit time codes, two bytes of time code information (frame/second/minute/hour), and one byte of error detection and correction code information. A more detailed example of the structure of the time code VITC is described in a book written by Keith Jack, entitled "Video Demystified", Hightext Publications, Inc., 1993, pp. 175-178. Such information is incorporated herein by reference.
When a video signal is edited, the time code information contained in the signal enables the editing process to be performed more efficiently. However, different broadcasting systems generate video signals which have line settings and characteristics which substantially differ depending upon the broadcasting systems. Accordingly, if a video time code generator is designed to generate a time code VITC in accordance with a particular broadcasting standard, the VITC information cannot be detected if the signal is transmitted in accordance with a different broadcasting standard. Accordingly, the signal cannot be efficiently edited, and thus, the compatibility between the time code generator and the various broadcasting systems is severely limited.